Glossary

22kW charging

Also known as 22 kW charging

22kW charging is EV charging at about 22 kilowatts, usually through a three-phase AC chargepoint.

7kW charging

Also known as 7.4kW charging, 7 kW charging

7kW charging is AC EV charging at about seven kilowatts, usually from a single-phase home chargepoint.

AC

Also known as Alternating current, AC

AC used by the UK mains supply, normal household circuits and grid-connected equipment.

AC charging

AC charging supplies AC to an EV, with the vehicle's onboard charger converting it to DC for the traction battery.

AC isolator placement

AC isolator placement describes where the AC isolator for an inverter circuit is positioned so the inverter can be disconnected from the grid-side AC supply.

AC-coupled battery architecture

AC-coupled battery architecture is a home-battery layout where a separate battery inverter connects the battery to a property's AC wiring, often alongside an existing solar inverter.

Access equipment

Access equipment is the scaffold, ladder, platform or other equipment used to let surveyors or installers reach an installation area safely during survey, installation, maintenance or removal.

Active network management

Also known as ANM

Active network management (ANM) is a network-control scheme that monitors electricity-network constraints and can reduce export or import from flexible connections when capacity is not available.

Air conditioning

Also known as AC

AC controls indoor temperature and, depending on the system, can provide cooling, heating, dehumidification and air circulation.

Air source heat pump

Also known as ASHP

An air source heat pump is a heat pump that collects heat from outside air and transfers it into the home for space heating, hot water or warm-air heating, depending on the system.

Air-to-air heat pumps

Air-to-air heat pumps move heat between outdoor air and room air, using indoor fan units for heating and, where the equipment is reversible, cooling.

Air-to-water heat pumps

Air-to-water heat pumps are air source heat pumps that extract heat from outside air and transfer it into a water-based heating circuit for space heating and domestic hot water.

Airtightness

Airtightness describes how strongly a building envelope resists uncontrolled air leakage through gaps, cracks and service penetrations when intended openings and ventilators are closed.

Alarm code

Also known as Alarm message, Fault code, Event code, Warning code

An alarm code is a number, label or app message that a home energy device uses to identify an alarm, warning, fault or operating condition.

Amp-hour

Also known as Ah, ampere-hour, ampere hour

Ah (amp-hour) is a unit of electric charge used in battery and equipment documents; in home energy it should be read with the battery voltage and the kWh (kilowatt-hour) capacity, not as a stand-alone runtime or power figure.

Annual consumption

Annual consumption is the amount of electricity or gas a household, meter point or fuel account uses over a year, usually shown in kilowatt hours.

Annual generation

Annual generation is the amount of electricity a generating system produces over a year, usually expressed in kilowatt hours.

Anti-islanding

Anti-islanding is the inverter or interface-protection function that stops grid-connected generation or storage from continuing to energise the network after the grid supply is lost.

Antifreeze

Antifreeze is a fluid additive or pre-mixed heat-transfer fluid used in a heat pump or heating loop to lower the water mixture's freezing point.

Arc fault detection device

Also known as AFDD

An AFDD (arc fault detection device) is a protective device in a consumer unit that detects arc-fault signatures and disconnects the affected circuit.

Array layout

An array layout is a drawing or plan that shows how solar PV modules are arranged on a roof, mounting frame or other installation area.

Array orientation

Array orientation is the compass direction a solar PV array faces, often recorded as an azimuth angle for generation estimates.

As-built drawing

An as-built drawing is a drawing or schematic updated at completion to show how an installation was actually built rather than only how it was originally designed.

Azimuth

Azimuth is the angle used to record the direction a solar PV surface faces against a stated reference direction.

Backfeed

Also known as back-feed, backfeeding, back feeding

Backfeed is electricity flowing from an on-site source back towards a circuit, consumer unit or electricity network rather than only from the grid supply to a load; in home energy it matters because solar, battery and vehicle-to-home systems can create two-way power flow.

Backup EPS output

A backup EPS output is the inverter output that can feed a dedicated socket, selected backup circuits or maintained loads during a grid outage when the system is installed for that use.

Backup heater

A backup heater is an additional heater, often electric, that can support a heat pump system for domestic hot water, low outdoor-temperature operation or fault and emergency modes when the product design allows it.

Backup immersion heater

A backup immersion heater is an electric heating element in a hot-water cylinder that can heat stored domestic hot water when the main heat source cannot cover demand or a control programme calls for direct electric heating.

Backup mode

Also known as Emergency power supply, EPS

Battery-storage operating mode for powering selected backed-up circuits during a grid supply failure, where the system has the required backup or EPS hardware.

Balance point

Balance point is the outdoor temperature at which a heat pump's available heating output matches the building's heat demand in a sizing or control calculation.

Ballast

Ballast is added weight used to hold equipment or a mounting frame in position, especially on flat-roof solar mounting systems.

Baseload

Also known as base load, base-load

Baseload is the lowest continuing level of electricity demand over a stated period; in home energy it is useful when separating always-on background use from short peaks caused by appliances, EV charging, heat pumps or battery charging.

Battery as a UPS substitute

Battery as a UPS substitute describes using a home battery backup arrangement in place of a dedicated uninterruptible power supply (UPS), with limits around transfer time, covered loads and product design.

Battery C-rate

Charge or discharge power expressed relative to usable battery capacity.

Battery calibration

Battery calibration is a manufacturer-supported process that helps a home battery system align its reported state of charge with the BMS's estimate of the energy stored.

Battery end-of-life recycling

Battery end-of-life recycling is the collection, handling and approved recycling route used when a home battery, battery module or battery pack is removed from service and is not being reused or repurposed.

Battery energy storage system

Also known as BESS

A battery energy storage system, often shortened to BESS, is the complete battery installation that stores electrical energy and returns it as electricity when the system controls call for it.

Battery expansion module

A battery expansion module is an additional battery unit fitted to a compatible home battery system to increase the system's usable storage capacity.

Battery fire rating

A battery fire rating is a shorthand label for fire-related battery safety evidence, such as a test standard, installation requirement or enclosure claim.

Battery firmware and cloud dependency

Battery firmware and cloud dependency describes how much a home battery system relies on manufacturer software, firmware updates, internet-connected apps or cloud services for monitoring, settings, schedules, diagnostics, remote control or support.

Battery inverter

A battery inverter is the power-electronics unit that connects a battery storage system to the AC side of a home energy installation.

Battery location and ventilation

Battery location and ventilation is the siting note that records where a home battery is installed and what airflow, clearance, temperature or fire-safety conditions apply.

Battery module

A battery module is a physical battery unit used as one building block of a modular home battery system.

Battery power rating

Battery power rating is the charge or discharge power a battery system is designed to handle, usually shown in kilowatts (kW) on datasheets, inverter documents and backup specifications.

Battery reserve

Also known as Backup reserve, Reserve level, Minimum SoC

Battery reserve is the part of a battery's state of charge that a system keeps back from ordinary discharge, usually for backup readiness or battery protection.

Battery stack

Also known as Stacked battery, Battery tower

A battery stack is a group of compatible battery modules installed and connected together so they operate as one storage battery unit.

Battery throughput

Also known as Energy throughput

Battery throughput is the cumulative amount of energy that passes into or out of a battery storage system over time.

Behind-the-meter vs in-front-of-meter

Also known as BTM, FTM, behind the meter, front-of-meter, front of meter

Behind-the-meter and in-front-of-meter describe which side of the electricity meter an energy asset sits on, separating on-site use from network-side supply or storage.

Bidirectional charging

Also known as Vehicle-to-grid charging, Vehicle-to-home charging, V2G, V2H, V2X

Bidirectional charging lets a compatible EV charger move electricity into an EV battery and, where supported, discharge energy back to a home, building or the grid.

Bifacial PV modules

Bifacial PV modules are solar panels designed to generate electricity from light reaching both the front and rear sides, so any extra output depends on reflected light, mounting and site conditions.

Billing period

A billing period is the date range covered by an energy bill, supplier statement or export payment statement.

Bird protection mesh

Bird protection mesh is a clipped or fixed barrier fitted around the edge of a solar PV array to reduce birds nesting or roosting underneath the panels.

Bivalent point and hybrid switchover

A bivalent point or hybrid switchover is the control condition in a hybrid heat-pump system that decides when a boiler or other supplementary heat source should help or take over from the heat pump.

Black start

Black start is the ability of a power system, generator, inverter or battery system to restart without an external electricity supply.

BMS (battery management system)

Also known as Battery management system, BMS

Battery system control and protection layer that monitors operating conditions and enforces manufacturer limits.

Boiler Upgrade Scheme

Also known as BUS

The Boiler Upgrade Scheme is an England and Wales grant scheme that helps eligible property owners reduce the upfront cost of replacing existing heating with a heat pump or biomass boiler.

Boundary distance

Boundary distance is the measured separation between equipment, an array or a cable route and a defined boundary or edge used in a planning, design, fire, noise or siting check.

Breaking capacity

Also known as fault rating

Breaking capacity is the fault-current rating that says how much short-circuit current a protective device is designed to interrupt safely.

BS 7671

Also known as IET Wiring Regulations, Wiring Regulations, 18th Edition

BS 7671 is the UK national standard for low-voltage electrical installations, commonly called the IET Wiring Regulations.

BS 9991 residential fire safety

Also known as BS 9991, BS 9991:2024

BS 9991 residential fire safety is a British Standard code of practice for fire safety in the design, management and use of residential buildings.

BS EN 50549 grid-connection standards

Also known as BS EN 50549, EN 50549, BS EN 50549-1, BS EN 50549-2

BS EN 50549 (British Standard adoption of European Standard 50549) grid-connection standards are British-adopted European standards for generating plants connected in parallel with distribution networks.

BS EN 62109-1 and 62109-2

Also known as BS EN 62109, EN 62109-1, EN 62109-2, IEC 62109-1, IEC 62109-2

BS EN 62109 (British Standard adoption of European Standard 62109) is the PV power-converter safety standard series behind general equipment and inverter-specific safety requirements.

Buffer tank

A buffer tank is a water vessel in a heating or heat pump circuit that adds heating-water volume and can keep heat pump flow separate from heating-circuit flow.

Building control notification

Building control notification is the record that relevant building work has been reported to building control or the local authority.

Building Regulations

Building Regulations are the building-control rules that apply to construction, extensions and relevant alterations.

C.O.P. / Coefficient of performance

Also known as Coefficient of performance, COP

Heat pump efficiency at a specific set of operating conditions, comparing useful heat output with electricity input.

C.T. clamp / Current transformer clamp

Also known as Current transformer clamp, CT clamp

Clip-on current transformer sensor used by monitors, inverters and chargers to measure AC current for import/export monitoring and load control.

Cable route

Also known as Cable run, Cable path, Cable routing

A cable route is the planned path a cable takes between parts of a home energy installation, including where it passes through or around the building.

CAN bus

Also known as CAN, Controller Area Network

A CAN (Controller Area Network) bus is a wired communications link that lets compatible controllers, batteries, inverters and monitoring devices exchange data.

Cancellation rights

Cancellation rights are the terms that explain when a customer can cancel a home-energy contract, quote acceptance or order and what happens to any deposit, advance payment or work already supplied.

Capacity retention

Also known as Energy retention, Retained capacity, Remaining usable capacity

Capacity retention describes how much of a battery's original usable capacity or nameplate rating remains available after age and use.

Capacity warranty

A capacity warranty is the part of a product warranty that promises a battery will retain at least a stated amount of usable or rated capacity for a defined period or use limit.

Cavity wall insulation

Cavity wall insulation is insulating material fitted into the gap between the inner and outer leaves of a cavity external wall to reduce heat loss through that wall.

CCS connector

Also known as Combined Charging System

A CCS connector is a Combined Charging System EV charging connector used for DC rapid charging, with the Combo 2 form specified for UK and European high-power public charging.

CCS rapid charging

CCS (Combined Charging System) rapid charging is DC EV charging through a CCS or Combo 2 connector, mainly on public rapid and ultra-rapid chargepoints.

Cell balancing

Cell balancing is the battery management process that keeps the cells in a battery pack at similar states of charge so one cell does not limit the pack before the others.

Cell voltage

Cell voltage is the electrical voltage of one battery cell inside a battery pack, usually monitored by the BMS to protect and balance the pack.

CHAdeMO

CHAdeMO is a DC EV fast-charging connector and protocol used by some vehicles and public rapid chargepoints, separate from CCS (Combined Charging System) and Type 2 AC charging.

Changeover switch

A changeover switch transfers backed-up circuits or a whole-property backup arrangement between the normal grid supply and a battery system's backup or EPS output.

Charge curve

A charge curve shows how an EV's charging power changes during a charging session, usually against state of charge or time.

Charge point management system

Also known as CPMS, EV charge point management system, Chargepoint management system

A charge point management system is the software platform used to monitor, configure and operate one or more EV chargepoints.

Charge power

Charge power is the rate at which a battery storage system can accept electricity while it is charging, normally shown in kilowatts.

Charge rate

Charge rate describes how quickly a battery is being charged compared with its usable capacity, usually as a C-rate or a limit inferred from kW or amp figures.

Charge schedule

A charge schedule is a control timetable that sets when a battery, EV chargepoint or another managed load is allowed or expected to charge.

Charge temperature limit

A charge temperature limit is the temperature range or threshold that decides when a home battery system is allowed to charge.

Chargepoint

A chargepoint is the EV charging unit, socket, wallbox or public charger that supplies electricity to a vehicle through a compatible cable or connector.

Charger cable routes and parking

Charger cable routes and parking describes how an EV chargepoint, charging lead and normal parking position line up so the cable can reach the vehicle without becoming a daily obstruction.

Circuit breaker

A circuit breaker is a resettable automatic protective device that disconnects a circuit when fault current or overload is detected.

Circulating pump

A circulating pump is a pump that moves water or heat-transfer fluid around a heating, hot-water or heat-pump circuit so heat can be carried between components.

Clearance

Clearance is the free space or distance left around equipment, an array, a boundary, a roof edge or another obstacle.

Clipping

Clipping is the flattening of a solar PV output trace when available generation is held at a limit instead of rising further.

Cloud API

Also known as Cloud application programming interface

A cloud API (application programming interface) is an internet-hosted software interface that lets authorised apps or services exchange data with a manufacturer's energy platform.

Commissioning flow rates

Commissioning flow rates are the water-flow readings checked during heat pump set-to-work to confirm that a heating circuit can move enough water for the selected operating mode.

Commissioning form

A commissioning form is a site-specific record used to capture the checks, test results or settings recorded when a home energy installation is put into working order.

Commissioning pack

A commissioning pack is the bundle of handover documents that records how a home energy installation has been set up, checked and handed over.

Communication fault

A communication fault is an error or status message showing that one part of a home energy system has stopped exchanging the expected data with another device, controller or online service.

Competent Person Scheme

A Competent Person Scheme lets a registered tradesperson self-certify specific building work instead of the homeowner applying for building regulations approval.

Condensate

Condensate is water produced when moisture in air or combustion gases turns back into liquid, usually needing a planned drain route.

Condensate drainage

Condensate drainage is the planned route that carries condensation or defrost water from a heat pump or other appliance to a suitable drain, soakaway, gully or run-off point.

Condensate pump

A condensate pump moves water from an AC indoor unit where a continuous gravity drain is not practical.

Connection agreement

Also known as DNO connection agreement, DNO connection authorisation

A connection agreement is written connection terms or DNO authorisation that records how a property, energy device or generation system may connect to the electricity network.

Connection application

Also known as DNO connection application, apply to connect

A connection application is a request or form submitted to a network operator or DNO before certain new connections, altered connections or home energy devices are connected.

Connection offer

Also known as DNO connection offer, electricity connection offer

A connection offer is a written offer, firm quote or set of connection terms from a network operator or DNO for making or changing an electricity connection.

Conservation area

A conservation area is a place designated for special architectural or historic interest, so exterior changes to a home energy installation may need extra local planning checks.

Consumer access device

Also known as CAD

A CAD (consumer access device) is a smart-meter accessory or built-in function that can access smart-meter data for an authorised display, app or service.

Consumer contract

A consumer contract is the legal agreement between a trader and a consumer for goods or services, including the contract behind a home-energy quote, order or installation.

Consumer unit

Also known as DB, Distribution board, Fuse board, Fuse box, Fusebox

A consumer unit is the domestic electrical board where the home's circuits are controlled, distributed and protected.

Consumer unit capacity

Also known as Fuse board capacity, Distribution board capacity

Consumer unit capacity is whether the domestic electrical board has space, suitable protection and board context for another circuit, not proof of spare supply capacity.

Consumption CT

Current-transformer sensor configured to measure household, site or circuit electricity consumption for monitoring, control or load calculations.

Cooling capacity

Also known as cooling output

Cooling capacity is the rate at which AC removes heat from a space, normally stated in kW.

Cooling load

Also known as room cooling load

Cooling load is the rate of heat that must be removed from a room or building to maintain the chosen indoor condition.

Credit meter

A credit meter is an electricity or gas meter, or smart-meter mode, where the supplier bills the household after energy has been used.

Current

Also known as A, amps, amperes

Current is the flow of electric charge, measured in amps, that appears in electrical ratings and limits for home energy equipment.

Current at maximum power

Also known as Imp

Current at maximum power is the PV module, string or array current at the maximum power point, usually shown as Imp in amps on solar datasheets.

Curtailment

Also known as output curtailment, export curtailment

Curtailment is the deliberate reduction or limiting of generation, export, import or controllable load below what the equipment could otherwise do.

Cycle life

Battery endurance rating that links repeated charging and discharging to usable-capacity loss under stated test or warranty conditions.

Cylinder coil

A cylinder coil is the heat-transfer coil or internal heat exchanger in an indirect hot water cylinder.

Data Communications Company

Also known as DCC

The Data Communications Company, usually shortened to DCC, operates the secure national communications network that connects smart meters with authorised energy-industry systems.

Data logger

A data logger is a device, gateway or built-in function that records operating data from equipment such as inverters, batteries, meters or sensors and passes it to a monitoring portal, local system or service platform.

Datasheet

A datasheet is a product document that summarises a manufacturer's technical ratings, limits, physical details and compliance information for a specific piece of equipment.

DC

Also known as Direct current, DC

DC used by solar panels, batteries, EV traction batteries and the DC side of inverter-based home energy systems.

DC charging

DC charging supplies DC to an EV, with the charger doing the AC-to-DC conversion before power reaches the vehicle battery path.

DC isolator placement

DC isolator placement describes where the DC isolation point for a PV array or string is positioned and documented in a solar installation.

DC leakage detection

DC leakage detection is an EV charger safety function that detects residual DC and triggers disconnection before it can impair upstream RCD protection.

DC to AC ratio

DC to AC ratio compares a solar PV array's rated DC size with the inverter's AC capacity.

DC-coupled battery architecture

DC-coupled battery architecture is a home-battery layout where solar PV generation and a compatible battery meet on the DC side of a hybrid inverter or similar power-conversion system.

Decibel A-weighting

Also known as dB(A)

Decibel A-weighting is the dB(A) sound-measurement notation used when a decibel figure has been adjusted with a frequency weighting that approximates the human ear's sensitivity.

Deemed export

Also known as deemed export payments

Deemed export is an estimated amount of electricity treated as exported, rather than a measured export reading.

Default off-peak charging

Default off-peak charging is a pre-set charging window on some private EV chargepoints, configured outside peak hours before the owner accepts, removes or changes it.

Default tariff

Also known as standard variable tariff

A default tariff is the supplier's standard variable tariff for imported energy when a household is not on a fixed or specialist tariff.

Defrost cycle

A defrost cycle is a normal operating mode in which an air source heat pump removes frost or ice from the outdoor coil so it can keep extracting heat from outside air.

Delta T / Flow and return temperature difference

Also known as Flow and return temperature difference, Delta T

Temperature difference used in heating design, especially the gap between flow and return water temperatures and radiator output ratings.

Demand forecast

A demand forecast estimates how much electricity a home, device group or wider electricity system is expected to use over a future period.

Demand response

Also known as DSR, Demand side response

Demand response is a deliberate change in electricity use at certain times, usually to reduce, shift or sometimes increase demand in response to prices, grid conditions or a flexibility service.

Deposit protection

Deposit protection is the arrangement that explains how a deposit or advance payment for home-energy work is protected before the installation is completed.

Depth of discharge

Usable battery-capacity window expressed as the share of stored energy discharged before recharging.

Design flow temperature

Design flow temperature is the maximum heating-water flow temperature used in a heating design at the chosen cold-weather design condition.

Design heat loss

Design heat loss is the calculated heat a room or property is expected to lose at the chosen design temperatures, used when sizing a heat pump and heat emitters.

Destination charging

Destination charging is EV charging at a place the driver has travelled to for another purpose, usually while the vehicle is parked for a visit, appointment or stay.

Direct debit

A direct debit is an authorised payment from a bank or building society account, often used by energy suppliers to collect regular account payments.

Discharge power

Discharge power is the rate at which a battery storage system can supply electricity while it is discharging, normally shown in kilowatts.

Discharge rate

Discharge rate describes how quickly a battery is being discharged compared with its usable capacity, usually as a C-rate or a limit inferred from kW or amp figures.

Discharge schedule

A discharge schedule is a control timetable that sets when a battery system is allowed or instructed to discharge.

Distribution network

The distribution network is the local electricity network of cables, overhead lines and substations that delivers electricity from the transmission system to homes and businesses.

Diversity

Also known as diversity factor, electrical diversity

Diversity is an electrical-design allowance for the fact that not every connected load is expected to draw its full rated current at the same time.

DNO (distribution network operator)

Also known as DNO

A DNO is the company responsible for the local electricity distribution network that carries electricity to homes and businesses in its area.

DNO approval letter

Also known as DNO authorisation, DNO connection approval

A DNO approval letter is written confirmation from the DNO that an apply-to-connect installation can go ahead, sometimes with stated amendments or connection conditions.

DNO notification

Also known as DNO registration, connect-and-notify

A DNO notification is the notice or record sent to the DNO so it knows about a home energy device or connection at a specific property.

Domestic hot water

Also known as DHW

Domestic hot water is the hot water supplied to taps, showers, baths and similar sanitary outlets in a home.

Double-pole isolation

Also known as DP isolator

Double-pole isolation is isolation that opens both the line/live conductor and neutral conductor of a single-phase AC circuit together.

Drainage

Drainage is the way rainwater, surface water, condensate or groundwater is collected, carried away or allowed to soak into a suitable part of a property.

Dynamic load balancing

Also known as DLB

Dynamic load balancing is an EV charging control that adjusts charging current or power against the property's available electrical capacity instead of using one fixed maximum rate.

Dynamic load balancing CT clamps

Dynamic load balancing CT (current transformer) clamps are sensors used by an EV chargepoint or load-management controller to measure site demand for dynamic load balancing.

Dynamic tariff

A dynamic tariff is an energy tariff where the price changes by time period, pricing formula or market signal rather than staying as one fixed unit rate.

Dynamic tariff API

Also known as Dynamic tariff application programming interface

A dynamic tariff API (application programming interface) is a software interface that lets apps or services retrieve dynamic tariff prices, product details or price windows from an energy supplier or platform.

Earth conductor

Also known as Protective conductor, CPC, Circuit protective conductor

An earth conductor is the protective earthing conductor that gives fault current a path to earth so protective devices can disconnect the circuit.

Earth electrode

Also known as Earth rod

An earth electrode is a conductor or group of conductors in contact with the ground that provides an electrical connection to earth.

Earth fault

Earth fault is an electrical fault where an accidental conductive path lets current flow between a live part and earth.

Earth fault loop impedance

Also known as Zs, fault loop impedance

Earth fault loop impedance is the impedance of the earth-fault path that affects how much fault current can flow before a protective device disconnects a circuit.

Earthing arrangement

An earthing arrangement describes how an electrical installation is connected to earth and how its protective earthing path is provided.

ECO4

Also known as Energy Company Obligation 4, Energy Company Obligation Phase 4

ECO4 (Energy Company Obligation 4) is the fourth Great Britain supplier-obligation scheme for improving energy efficiency and heating in eligible low-income, fuel-poor or vulnerable homes.

Economy 10

Economy 10 is a multi-rate electricity import tariff with ten lower-rate off-peak hours in each 24-hour period, usually split across more than one time window.

Economy 7

Economy 7 is a multi-rate electricity tariff with a cheaper off-peak period, usually seven hours overnight, and a higher peak rate for the rest of the day.

EER

Also known as energy efficiency ratio

EER is the ratio of cooling output to electrical input at stated rating conditions.

Electrical Installation Certificate

Also known as EIC

An Electrical Installation Certificate records the BS 7671 inspection and testing for electrical installation work covered by the certificate.

Electrical Installation Condition Report

Also known as EICR

An Electrical Installation Condition Report records the condition of an existing electrical installation after inspection and testing.

Electrical supply for heat pumps

Electrical supply for heat pumps is the property-side circuit, connection-capacity and network-supply context checked before a heat pump is connected.

Emitter

An emitter is the part of a heating system that releases heat into a room, such as a radiator, fan convector or underfloor heating loop.

ENA Type Test Register

The ENA Type Test Register is the register where manufacturers record type-tested generating equipment and system references used in GB G98 and G99 connection paperwork.

End of life

Also known as EOL

End of life is the point at which a home battery, battery module or related component is treated as no longer suitable for its intended service, usually because age, cycling, capacity loss, faults or manufacturer support limits have made replacement or disposal necessary.

Energy

Also known as electrical energy, stored energy

Energy is the amount of electricity or heat used, generated, stored or delivered over time, usually shown in home energy documents in kWh.

Energy gateway hardware

Energy gateway hardware is the gateway, system controller or backup interface that coordinates metering, isolation, backup switching or load control around a home battery system.

Energy Performance Certificate

Also known as EPC

An Energy Performance Certificate rates a property's energy efficiency and records recommended improvement measures for the building.

Engineering Recommendation

Also known as EREC

An Engineering Recommendation is an ENA technical document, often shortened to EREC (Engineering Recommendation), that sets requirements or guidance used in Great Britain electricity-network engineering.

EPS (emergency power supply)

Also known as EPS

EPS is the backup-output function on some battery inverter systems that can keep a dedicated socket or selected circuits powered during a grid outage.

Equipotential bonding

Also known as Bonding, Protective bonding

Equipotential bonding is an electrical safety measure that connects specified conductive parts to reduce voltage differences during a fault.

Essential loads

Essential loads are the selected loads, circuits or sockets that a battery backup arrangement is intended to keep supplied during a grid outage.

Estimate

An estimate is a provisional best guess of likely cost, work, output or energy use, rather than a fixed quote or guarantee.

Estimated reading

An estimated reading is a meter reading value an energy supplier has calculated because it does not have an actual smart, customer or meter-reader reading for that point in the billing period.

EV chargepoint commissioning

EV chargepoint commissioning is the final setup, testing and recording work that checks a chargepoint has been configured and handed over for its specific site.

EV charger throttling

EV charger throttling is a reduction or pause in charging current or power when a chargepoint, vehicle or control system gives another limit priority.

Event log

Also known as Event history, System event log, System log, Fault log

An event log is a time-ordered record of system events, alarms, setting changes or communication changes kept by a home energy device, app or monitoring platform.

EVSE

Also known as Electric vehicle supply equipment

EVSE means EV supply equipment: the charging equipment that supplies electricity to an EV through a socket, connector, cable or chargepoint.

Expansion vessel

An expansion vessel is a vessel that gives heated water room to expand in a sealed hot water or heating system.

Export

Also known as electricity export, exported electricity, solar export, grid export

Export is electricity sent from a home energy system to the electricity network instead of being used on site or stored.

Export capacity

Export capacity is the amount of power a property or installation is allowed to send to the electricity network under its DNO connection arrangement.

Export CT

Current-transformer sensor used by an inverter, battery system or site controller to measure export power near the grid connection point.

Export limit

An export limit is the cap on how much power an installation is allowed or set to send to the electricity network.

Export limitation with batteries

Export limitation with batteries is the control arrangement that keeps battery discharge from pushing a property above its DNO agreed export limit.

Export MPAN

Also known as Export Meter Point Administration Number, Export MPAN

Metering-point identifier used to register and pay for measured electricity exported to the grid.

Export permission

DNO authorisation, connection terms or a completed notification route that lets a site export electricity to the distribution network within stated conditions or limits.

Export rate

An export rate is the price paid for each kilowatt hour of electricity a household exports to the grid under an export or SEG (Smart Export Guarantee) tariff.

Export settlement

Export settlement is the process of using export meter readings and supplier tariff terms to calculate or reconcile electricity sent from a small-scale generator to the grid.

Export tariff

An export tariff is an energy-supplier tariff that pays an eligible household or small-scale generator for electricity exported to the grid.

F-gas

F-gas is shorthand for fluorinated greenhouse gas, a group of gases that includes HFC refrigerants used in some heat pumps and air-conditioning systems.

F-gas qualification rules

F-gas (fluorinated greenhouse gas) qualification rules are legal rules that require the right personal qualifications, and sometimes company certification, before work is carried out on equipment containing F-gas.

Failsafe export limitation

Also known as fail-safe export limitation

Failsafe export limitation is fallback behaviour in a G100 (Engineering Recommendation G100) export-limiting scheme, used to keep export within a DNO agreed limit if a control component or communication path fails.

Fan convector

A fan convector is a heat emitter that uses a fan to move room air across heated fins or a coil, helping a compact unit release heat into the room.

Feed-in Tariff

Also known as FIT

The Feed-in Tariff (FIT) is a closed Great Britain scheme that pays accredited small-scale low-carbon generators for electricity they generate and, where eligible, export.

Fire stopping

Fire stopping is the sealing of joints, gaps and service openings through a fire-resisting or fire-separating part of a building so its fire resistance is not weakened.

Firefighter PV isolation

Firefighter PV isolation is the isolation, labelling and emergency information that helps fire and rescue crews understand which parts of a solar PV system can be switched off and which DC parts may remain live.

Firmware

Firmware is the built-in software in a device, such as an inverter, battery controller or gateway, that controls how the hardware operates.

Firmware version

Firmware version is the release identifier for the built-in software running inside equipment such as an inverter, battery controller, EV chargepoint, gateway or heat-pump control.

Fixed tariff

A fixed tariff is an energy import tariff where the unit rate, and usually the standing charge, stay the same for a set contract period.

Flat-rate tariff

A flat-rate tariff is an energy tariff where the relevant units are charged or paid at one unit rate instead of changing by peak, off-peak or half-hourly time bands.

Flexible load

Also known as flexible demand, controllable load

A flexible load is an electrical demand that can be shifted, delayed, reduced or controlled within limits instead of always using power immediately.

Flow rate

Flow rate is how quickly water or heat-transfer fluid moves through a heating circuit, which affects whether a heat pump and its emitters can move the intended heat.

Flow temperature

Flow temperature is the temperature of the heating water as it leaves a heat source or heating circuit and travels towards radiators, underfloor heating or other heat emitters.

Force charge mode

Force charge mode is an app or inverter operating mode that tells a battery system to charge during a selected window or until a configured state of charge is reached.

Forced charge

Also known as Force charge, Forced charging

Forced charge is a battery or inverter control that commands the battery to charge during a defined period or until a target state of charge is reached.

Frost protection

Frost protection is the design, control or installation measure used to reduce the risk of water, condensate drains, pipework or outdoor equipment freezing in cold conditions.

Fuse

A fuse is an overcurrent protective device that opens a circuit when fault or overload current melts its fuse element.

G100 export limitation

G100 export limitation is an export-control arrangement that keeps power exported from a property within a DNO-agreed limit under ENA Engineering Recommendation G100.

G83 and G59 legacy connection routes

Also known as G83 and G59 legacy routes

Legacy GB distribution-network connection standards that preceded G98 and G99 for generation such as solar PV, batteries and inverters.

G98 notification

A G98 notification is the post-installation notice sent to a DNO for an eligible small generation or export-capable storage installation that uses Engineering Recommendation G98.

G98 notification pathway

G98 notification pathway is the connect-and-notify grid-connection route for eligible small generation or export-capable storage equipment under ENA Engineering Recommendation G98.

G99 application

Also known as EREC G99 application, G99 application form

A G99 application is an apply-to-connect submission sent to a DNO before certain generation, storage or export-capable equipment is installed or commissioned under ENA Engineering Recommendation G99.

Gateway

Also known as System gateway, Monitoring gateway, Communication gateway

A gateway is a device, product module or controller function that links home energy equipment to monitoring, metering, backup control or an internet-connected app or platform.

GDPR and energy data

GDPR (General Data Protection Regulation) and energy data describes how UK data-protection rules apply when personal energy records are collected, used or shared.

Generation CT

Current-transformer sensor configured to measure output from a solar PV, wind or other generation circuit for monitoring or control.

Generation meter

A generation meter records the electricity generated by a solar PV installation or another small-scale renewable electricity system, separately from import and export meter readings.

Global warming potential

Also known as GWP

Global warming potential is a relative measure of how much a gas contributes to global warming compared with carbon dioxide.

Glycol

Glycol is a heat-transfer-fluid ingredient, usually propylene glycol or ethylene glycol, used with water in some heat pump and heating circuits for freeze protection.

Granny charger

A granny charger is the informal name for a portable EV charging lead used with a standard 3-pin socket rather than a fixed home chargepoint.

Great British Insulation Scheme

Also known as GBIS, ECO+

The Great British Insulation Scheme was a Great Britain energy-efficiency supplier-obligation scheme for free or cheaper insulation in eligible less efficient homes.

Grid charge permission

Product-control setting that allows a home battery system to charge from imported grid electricity rather than only from on-site generation.

Grid charging

Grid charging means charging a home battery from imported grid electricity rather than from on-site generation such as solar PV.

Grid-following

Grid-following describes inverter control that synchronises with an existing AC grid waveform rather than forming its own voltage reference.

Grid-forming

Grid-forming describes inverter control that can establish and regulate an AC voltage and frequency reference rather than only following an existing grid waveform.

Grid-tied inverter

Also known as grid-connected inverter

A grid-tied inverter is an inverter designed to operate in parallel with the public electricity network rather than as a stand-alone power source.

Ground source heat pump

Also known as GSHP

A ground source heat pump is a heat pump that collects low-temperature heat from the ground through buried pipework or boreholes.

Half-hourly data

Also known as HH data

Half-hourly data is smart-meter or meter-settlement data split into 30-minute periods, usually used to match import or export readings with smart tariff prices and billing periods.

Handover pack

A handover pack is the set of documents and operating information given to the customer when a home energy installation is completed and handed over.

Handover settings and user controls

Handover settings and user controls are the customer-facing heat pump or heating-control settings explained when the system is commissioned and handed over.

Heat curve

Also known as weather compensation curve, heating curve, weather curve

A heat curve is a weather-compensation setting that links outdoor temperature to the heating flow temperature a heat pump or controller should target.

Heat exchanger

A heat exchanger is a component that passes heat from one fluid, gas or circuit to another without the two flows normally mixing.

Heat load

Heat load is the calculated rate of heat a room or property needs from the heating system under specified design conditions.

Heat loss

Heat loss is the rate at which heat leaves a room or property through the building fabric, ventilation and air leakage.

Heat loss report

Also known as heat loss calculation report, heat load report, heat load calculation report

A heat loss report is the document or exported report from a heat loss or heat load calculation, used to show the heat demand assumptions behind a heat pump design.

Heat loss survey

Also known as heat load survey, room-by-room heat loss survey

A heat loss survey is the room-by-room property assessment that gathers the details used to calculate heat loss for a heat pump design.

Heat networks and district heating

Heat networks and district heating describe shared systems that move heat from a central or local source to multiple homes, buildings or sites instead of each dwelling having its own heat source.

Heat pump sizing margin

Heat pump sizing margin is the allowance between a calculated design heat load and the selected heat pump and emitter output.

Henley block

Also known as Service connector block

A Henley block is a service connector block used in the meter and intake area to split or join meter-tail conductors, not proof that the supply is suitable for extra equipment.

Hertz

Also known as Hz, frequency

Hertz is the unit used to state frequency, with one hertz meaning one cycle per second.

HIES

Also known as Home Insulation and Energy Systems, Home Insulation and Energy Systems Contractors Scheme, HIES Consumer Code, HIES Quality Assured Contractors Scheme

HIES (Home Insulation and Energy Systems) is a consumer-protection scheme for businesses installing renewable energy and home energy efficiency products in domestic properties.

Home area network

Also known as HAN

A HAN (home area network) is the smart-meter network inside a property that lets the communications hub, smart meters, an in-home display and authorised devices exchange data.

Home charger

A home charger is a common name for an EV chargepoint installed at a home so an EV can charge from the property's electrical supply rather than from a public charger.

Home energy management system

Also known as HEMS

A home energy management system is the software, hardware or control platform that monitors and coordinates compatible energy devices in a home.

Home Energy Scotland funding

Also known as Home Energy Scotland Grant and Loan, HES grant and loan

Home Energy Scotland funding is Scottish Government-funded grant or interest-free loan support for eligible homeowners in Scotland, accessed through Home Energy Scotland advice and referral.

Hot water cylinder

Also known as DHW cylinder, domestic hot water cylinder

A hot water cylinder is an insulated storage vessel that holds domestic hot water for taps, showers and baths until it is needed.

Hot water priority control

Also known as Hot water priority, DHW priority, Domestic hot water priority

Hot water priority control is a heat pump control behaviour that gives cylinder reheating priority over space heating.

Hub

Also known as Smart home hub, Control hub, Device hub

A hub is a device, built-in module or controller role that connects compatible home energy products or smart-home devices to an app, platform or network.

Hybrid heat pump systems

Hybrid heat pump systems combine a heat pump with another heat source, usually a boiler, under controls that decide when each source supplies heating or hot water.

Hybrid inverter

A hybrid inverter is an inverter that works with both solar PV and battery storage, converting DC electricity and controlling battery charging or discharging within the unit's design limits.

Hydraulic balancing

Hydraulic balancing is the commissioning process that sets water flow through heating circuits so each radiator, underfloor loop or emitter receives the flow needed for the design heat output.

Hydraulic separation

Hydraulic separation is the wet-heating design principle that lets two water circuits with their own pumps exchange heat without one circuit's pump forcing unstable flow through the other.

ICCB on Mode 2 leads

An ICCB (in-cable control box) is the control and protection box built into a Mode 2 EV charging lead between the supply plug and the vehicle connector.

IDNO (independent distribution network operator)

Also known as IDNO

An IDNO (independent DNO) is a licensed electricity DNO that owns and operates a smaller local network connected to a host DNO network.

IET EESS Code of Practice

Also known as IET Code of Practice for Electrical Energy Storage Systems, Code of Practice for Electrical Energy Storage Systems

The IET (Institution of Engineering and Technology) EESS (electrical energy storage systems) Code of Practice is practitioner guidance for fixed battery storage and other electrical energy storage installations.

IET EV charging code

Also known as IET Code of Practice for Electric Vehicle Charging Equipment Installation, Code of Practice for Electric Vehicle Charging Equipment Installation, IET EV charging Code of Practice

The IET (Institution of Engineering and Technology) EV charging code is practitioner guidance for planning, installing, inspecting and testing EV charging equipment.

Immersion boost

Also known as DHW immersion boost, manual boost

Immersion boost is a temporary control mode that runs an immersion heater to add direct electric heat, usually for a hot water cylinder.

Impedance

Impedance is the opposition an AC circuit, cable or device presents to current flow, measured in ohms.

Import

Also known as electricity import, imported electricity, grid import

Import is electricity taken from the electricity network into a property or installation.

Import capacity

Import capacity is the amount of power a property or installation is allowed to take from the electricity network under its connection arrangement.

Import limit

An import limit is a cap on how much power a property, device or control scheme is allowed or set to take from the electricity network.

Import MPAN

Also known as Import Meter Point Administration Number, Import MPAN

An import MPAN is the electricity-supply identifier used for electricity imported from the grid at a property.

Import rate

An import rate is the price charged for each kilowatt hour of electricity a household imports from the grid under its energy tariff.

In-home display

Also known as IHD

An in-home display is the small portable screen paired with a smart meter that shows recent energy use, cost and, for prepayment meters, credit information inside the home.

In-roof solar mounting

Also known as Roof-integrated solar mounting, Roof integrated solar mounting, In-roof PV mounting

In-roof solar mounting is a pitched-roof solar PV mounting approach where the panels and flashing kit sit in the roof covering rather than above it on rails.

Indoor unit

Also known as AC head, fan unit

An indoor unit is the part of a split AC or air-to-air heat-pump system that transfers heat to or from room air.

Inrush current

Inrush current is the short surge of current a device can draw when it is first energised, before it settles to normal running current.

Insolation

Also known as solar insolation, solar irradiation

Insolation is the solar energy received by a surface over a stated period, usually expressed as kWh/m² (kilowatt hours per square metre) for a roof plane, PV array or location.

Installation manual

An installation manual is a manufacturer document that explains how a specific product or system should be installed, connected, commissioned and handed over.

Insulation resistance

Also known as IR test

Insulation resistance is a measured electrical resistance value used to check how well conductors are insulated from each other and from earth.

Inverter clipping

Inverter clipping is output limiting that happens when a solar PV array could supply more DC power than the inverter can convert or deliver at that moment.

Inverter efficiency

Inverter efficiency describes how much electrical energy remains after an inverter converts electricity between DC and AC.

Inverter start-up voltage

Also known as start-up voltage, feed-in start voltage

Inverter start-up voltage is the DC PV input voltage a solar or hybrid inverter needs before it can start operating from a string.

IP rating

Also known as Ingress protection rating, IP code

An IP rating is an enclosure code that states protection against solid objects such as dust and against water ingress.

Irradiance

Also known as solar irradiance

Irradiance is the solar power arriving on a surface at a particular moment, usually measured in watts per square metre.

Island mode

Also known as Island-mode operation

Island mode is the operating state where a battery storage system supplies selected circuits while that part of the installation is isolated from the grid.

Islanding

Islanding is the condition where part of an electrical installation or network remains energised while separated from the public electricity grid.

ISO 15118

ISO (International Organization for Standardization) 15118 is a family of EV to chargepoint communication standards that supports features such as Plug & Charge, smart charging and bidirectional charging where compatible equipment supports them.

Isolator

Also known as Isolation switch

An isolator is a switch or device used to disconnect an electrical supply from equipment, a circuit or another part of an installation.

Kilovolt-ampere

Also known as kVA, kilovolt ampere, kilovolt amps

A kilovolt-ampere, or kVA, is 1,000 volt-amperes and is used for apparent power or electrical capacity in AC systems.

kW / Kilowatt

Also known as Kilowatt, kW

Unit of power for instantaneous electricity use, generation, charging and discharge in home energy documents.

kWh / Kilowatt-hour

Also known as Kilowatt-hour, kWh

Unit of energy for electricity consumption, storage, generation, export and charging over time.

kWp / Kilowatt peak

Also known as Kilowatt peak, kWp

Solar PV peak power rating under standard test conditions for comparing panels, arrays and expected generation.

Legacy FIT repowering

Also known as FIT repowering, Repowering a FIT installation

Legacy FIT (Feed-in Tariff) repowering means replacing older accredited generating equipment where the work may affect capacity, metering, notification duties or payment treatment under the closed FIT scheme.

Legionella cycle

A Legionella cycle is a scheduled hot-water control cycle that periodically raises a domestic hot water cylinder temperature as part of bacterial-growth control.

LFP

Also known as LiFePO4

LFP, also written LiFePO4, is a lithium-ion battery chemistry used in home battery storage systems.

Listed building

A listed building is a building or structure protected for special architectural or historic interest, so home energy work may need listed building consent or extra planning checks.

Lithium-ion battery

Also known as Li-ion

A lithium-ion battery is a rechargeable battery type that moves lithium ions between electrodes as it charges and discharges.

Live conductor

Also known as Line conductor

Live-conductor wording identifies a conductor role or condition in electrical paperwork, not a sign that a circuit is safe, isolated or suitable to work on.

Load compensation controls

Also known as Load compensation, Room influence

Load compensation controls use indoor temperature feedback to adjust the heat sent into a heating system.

Load profile

Also known as electricity load profile, demand profile, usage profile

A load profile is a demand-over-time view used to understand when a home imports electricity, runs large loads or has flexible demand.

Load profile class

Also known as Profile Class, electricity profile class, settlement profile class

A load profile class is an electricity-settlement category that groups similar customers so non-half-hourly consumption can be assigned a representative pattern over time.

Load shedding

Load shedding is the deliberate switching off or disconnection of selected electrical loads so a supply, backup output or connection stays within its limits.

Load shedding gateway

A load shedding gateway is a backup-battery gateway or controller that can disconnect selected loads when a home battery system is running with limited backup power.

Local API

Also known as Local application programming interface

A local API (application programming interface) is a software interface that lets authorised apps or controllers exchange data with equipment over the property's local network.

Loft insulation

Loft insulation is insulation fitted at loft or roof-space level, usually above the top-floor ceiling or between roof rafters, to reduce heat loss through the roof area.

Looped electricity supplies

Also known as Looped supply, Looped service, Looped connection, Shared service cable

Looped electricity supplies are shared incoming service-cable arrangements where two or more properties take electricity through the same connection from the local network.

Low-loss header

A low-loss header is a heating-system hydraulic separator that lets primary and secondary water circuits work with little pump interference.

Low-temperature charging

Low-temperature charging is charging attempted when a battery is below the temperature range its manufacturer allows for normal charging.

M.P.A.N. Core / MPAN Core

Also known as MPAN Core, 13-digit MPAN

MPAN Core is the 13-digit part of an MPAN used as the industry reference for a particular electricity metering point.

Main fuse

Also known as Cut-out fuse, Service fuse

Main-fuse wording refers to the incoming supply fuse or cut-out fuse, not proof that the home has spare electrical capacity for new equipment.

Main fuse protection

Also known as Main fuse monitoring

Main fuse protection is an EV charging or load-management control that limits charging against the rating of the property's main electrical fuse.

Main protective bonding

Also known as Main bonding, Main earth bonding

Main protective bonding connects incoming metal services or other extraneous conductive parts to the main earthing terminal so touch voltages are reduced during a fault.

Maintenance schedule

Also known as Servicing schedule, Service schedule

A maintenance schedule is a written list of recommended checks, servicing tasks and intervals for an installed home energy system.

Maximum demand

Also known as MD

Maximum demand is the highest electrical load a property or installation is expected to place on the supply at one time.

Maximum export capacity

Maximum export capacity is the agreed upper limit on the rate of electricity a property connection may export to the distribution network.

Maximum import capacity

Also known as MIC

Maximum import capacity is the agreed upper limit on the rate of electricity a property connection may import from the distribution network.

Maximum input current

Maximum input current is the highest current a specified inverter input is designed to accept, usually shown in amps on a solar or hybrid inverter datasheet.

Maximum output current

Maximum output current is the highest current a specified inverter output or AC terminal is rated to deliver under stated conditions, usually shown in amps on inverter and battery-system datasheets.

Maximum power point

Also known as MPP

The maximum power point is the voltage and current combination where a solar PV module, string or array produces its highest power under the conditions at that moment.

MCB / Miniature circuit breaker

Also known as Miniature circuit breaker, MCB

Miniature circuit breaker for overcurrent protection in consumer-unit and distribution-board circuits.

MCS

Also known as Microgeneration Certification Scheme

MCS is the UK quality mark and certification scheme for small-scale renewable and low-carbon systems such as solar PV, heat pumps and battery storage.

MCS 012 solar mounting standard

Also known as MCS 012, Solar Mounting Product Standard, MCS 012 Solar Mounting

MCS 012 is the MCS solar mounting product standard for certifying roof mounting systems and components used to attach solar PV or solar thermal panels to building roofs.

MCS 020

MCS 020 is the MCS sound-calculation standard used to check whether an air source heat pump meets the permitted development noise limit at neighbouring assessment positions.

MCS 031

Also known as MCS 031 a), Heat pump system performance estimate standard

MCS 031 is the MCS heat pump pre-sale information and system performance estimate standard used to produce a comparable annual performance estimate before a contract is awarded.

MCS compliance certificate

Also known as MCS certificate

An MCS compliance certificate is the MCS certificate that records a certified renewable or low-carbon installation after it has been designed, installed and commissioned under the MCS scheme.

MCS installation standards

MCS installation standards are the MCS technical rules that describe how certified contractors should design, install, commission and hand over eligible small-scale renewable or low-carbon systems.

MCS performance estimate

Also known as Solar PV performance estimate, MCS PV performance estimate

An MCS performance estimate is a pre-contract solar PV calculation that estimates annual generation and, where relevant, self-consumption using the MCS method rather than promising actual output.

Mechanical ventilation with heat recovery

Also known as MVHR

Mechanical ventilation with heat recovery (MVHR) is a whole-dwelling ventilation system that supplies fresh air, extracts stale or humid air and transfers some heat from outgoing air into incoming air through a heat exchanger.

Meter integration

Meter integration is the link that lets an app, controller or home energy device use readings from a meter, energy meter or metering interface.

Meter Point Reference Number / MPRN

Also known as MPRN

An MPRN (Meter Point Reference Number) is the gas supply point identifier used by suppliers and gas-industry systems for a property.

Meter reading

A meter reading is the value recorded from a gas or electricity meter at a point in time, used with other readings to work out energy used, energy exported or account charges.

Meter serial number / MSN

Also known as MSN, Meter ID

A meter serial number (MSN) is the unique reference printed on a gas or electricity meter that identifies that physical meter, separate from the supply point numbers tied to the property.

Meter tails

Meter tails are the supply-side cables between the electricity meter area and the consumer unit or intake equipment, not proof that the supply is suitable for new home energy equipment.

Metered export

Metered export is electricity sent from a small-scale generation installation to the grid and recorded by a meter or export register rather than estimated as deemed export.

Microinverter

Also known as Solar microinverter, Module-level inverter

A microinverter is a small solar inverter fitted at panel level so each module converts DC output into AC electricity.

Mini-split

Also known as mini split, ductless mini-split

A mini-split is a fixed split AC or air-to-air heat-pump arrangement with an outdoor unit and one or more indoor units.

Minor Electrical Installation Works Certificate

Also known as MEIWC

A MEIWC (Minor Electrical Installation Works Certificate) records BS 7671 certification for minor electrical work that changes an existing circuit without adding a new circuit.

MIS 3002

Also known as The Solar PV Standard, The Solar PV Installation Standard, MIS 3002 solar PV standard

MIS 3002 is the MCS installation standard for solar PV systems fitted by MCS certified contractors.

MIS 3005 heat pump standard

Also known as MIS 3005, The Heat Pump Standard, MIS 3005-D, MIS 3005-I

MIS 3005 is the MCS heat pump standard family for MCS certified heat pump contractors, split into design and installation standards under MCS:2025.

MIS 3012 battery storage standard

Also known as MIS 3012, The Battery Installation Standard, Battery Installation Standard

MIS 3012 is the MCS battery storage installation standard for MCS certified contractors working on EESS (electrical energy storage systems).

Mismatch loss

Also known as module mismatch loss, array mismatch loss

Mismatch loss is solar PV output lost when modules, strings or array sections connected together cannot all operate at their own maximum power point because their electrical conditions differ.

Modbus

Modbus is a register-based communications protocol used by compatible inverters, batteries, meters and gateways to exchange readings or control values, often as Modbus TCP (Transmission Control Protocol) or Modbus RTU (remote terminal unit).

Mode 2 charging

Mode 2 charging is EV charging from a socket using a portable cable with in-cable control and protection between the supply and the vehicle.

Mode 3 charging

Mode 3 charging is EV charging through a dedicated AC chargepoint or EV supply equipment, usually using a chargepoint socket or tethered cable rather than a portable socket lead.

Modulation

Modulation is a heat pump's ability to vary its heating output within a range instead of only running at one fixed output or switching fully off.

Module efficiency

Module efficiency is the percentage of sunlight falling on a solar PV module that the module converts into electrical power under stated test conditions.

Monitoring portal

A monitoring portal is the app, web dashboard or account interface used to view a home energy system's status, readings, alerts and, where the product allows, control settings.

Monitoring portal data

Monitoring portal data is the readings, status records and event information shown in a solar, inverter or battery app or web portal.

Monobloc

A monobloc heat pump is an air-to-water heat pump where the main heat pump equipment is packaged as one outdoor unit connected to the home's heating system by flow and return water pipework.

Monocrystalline PV modules

Also known as Monocrystalline solar panels, Mono PV modules

Monocrystalline PV modules are solar panels whose cells are made from single-crystal silicon wafers.

MPAN (meter point administration number)

Also known as MPAN, Supply number, S number

An MPAN is an electricity identifier for a metering point or supply point on the distribution network.

MPPT (maximum power point tracker)

Also known as Maximum power point tracking, MPPT

MPPT in solar inverters, hybrid inverters and related PV electronics.

MPPT voltage range

MPPT voltage range is the DC voltage window in which an inverter's MPPT is designed to operate.

Multi-split system

Also known as multi split

A multi-split system connects several compatible indoor AC units to one outdoor unit.

NAPIT

Also known as National Association of Professional Inspectors and Testers

NAPIT (National Association of Professional Inspectors and Testers) is a UKAS (United Kingdom Accreditation Service) accredited certification and membership scheme operator that can appear in home energy paperwork.

National Energy System Operator

Also known as NESO

The National Energy System Operator is Great Britain's public energy-system operator and planner, responsible for balancing the electricity system and shaping future electricity and gas system planning.

Neighbour receptor

A neighbour receptor is the neighbouring property, habitable-room opening or outdoor amenity area that a planning, noise or siting assessment treats as the place that could receive an effect from proposed home energy equipment or works.

Nest Warm Homes Wales

Also known as Welsh Government Warm Homes Nest scheme, Nest scheme, Warm Homes Nest

Nest Warm Homes Wales is the Welsh Government Warm Homes Nest scheme, offering free impartial home energy advice and, for eligible lower-income households in Wales, a package of free home energy efficiency improvements.

Neutral conductor

Neutral-conductor wording identifies the neutral side of an AC supply or circuit, not a sign that a circuit is safe, isolated or suitable for new equipment.

Neutral switching

Neutral switching is a backup-system control or relay arrangement that changes the neutral connection when a battery system moves between grid-connected operation and island-mode backup.

NICEIC

Also known as National Inspection Council for Electrical Installation Contracting

NICEIC (National Inspection Council for Electrical Installation Contracting) is a UK certification and assessment brand for electrical businesses and related trades that can appear in home energy paperwork.

NMC battery chemistry

Also known as Lithium nickel manganese cobalt oxide, Lithium nickel manganese cobalt oxide battery chemistry

NMC (lithium nickel manganese cobalt oxide) battery chemistry is a lithium-ion cell chemistry that uses nickel, manganese and cobalt in the positive electrode.

Noise assessment

A noise assessment is a check of predicted or measured sound from equipment, used to judge whether an installation is likely to meet a planning, permitted development or local amenity requirement.

Nominal capacity

Also known as Nameplate capacity, Rated capacity

Nominal capacity is the nameplate energy size of a battery when new, before usable-capacity and operating limits are applied.

Nominal operating cell temperature

Also known as NOCT, NMOT

NOCT (Nominal Operating Cell Temperature) is a solar module datasheet value for the cell temperature reached under defined outdoor test conditions.

Nominal power

Nominal power is the rated power level a device is designed to deliver under stated normal conditions, usually shown in watts or kilowatts on an inverter or battery datasheet.

OCPP (Open Charge Point Protocol)

Also known as Open Charge Point Protocol, OCPP

OCPP communication between EV charge points and charge-point management systems.

Off-peak rate

An off-peak rate is the lower unit price that applies to electricity used during specified lower-demand periods on a multi-rate or time-of-use tariff.

Open PEN fault

Also known as PEN fault

An open PEN fault is a distribution-network fault involving a combined PEN conductor, not proof that a home charger, inverter or circuit is defective.

Open PEN protection

Also known as Open PEN conductor protection, OPDD

Open PEN protection is EV charging protection that disconnects the chargepoint and vehicle when it detects a dangerous open PEN conductor fault on a PME supply.

Open-circuit voltage

Also known as Voc

Open-circuit voltage is the voltage at a solar PV module, string or array when it is illuminated but not delivering current to a load or inverter.

Open-loop GSHP

Also known as Open-loop ground source heat pump, Open loop ground source heat pump, Open loop GSHP

An open-loop GSHP (ground source heat pump) is a heat pump arrangement that abstracts groundwater, uses it as a heat source or heat sink and returns it to ground or surface water.

Operating mode

Operating mode is a device or system control label that describes how home energy equipment is set to run, such as heating, cooling, charging, discharging, standby or fault operation.

Outdoor unit siting

Outdoor unit siting is the choice and recorded position of a heat pump outdoor unit, taking account of airflow, service access, sound, drainage, visual impact and planning or manufacturer constraints.

Outside design temperature

Also known as design outside temperature, design external temperature, DOT (design outside temperature)

Outside design temperature is the outdoor temperature used as the cold design point for heat loss calculations and heat pump sizing checks.

Over-the-air update

Also known as OTA update, Remote firmware update, Remote online firmware update

An OTA (over-the-air) update is a software or firmware update delivered to compatible home energy equipment through a network connection rather than a local USB (Universal Serial Bus) file or service tool.

Overload

Also known as Overload current

Overload is an overcurrent condition where a circuit or item of equipment is carrying more current than its limit allows, without being a short circuit or earth fault.

Oversizing

Oversizing is sizing one part of a solar PV design above a chosen reference value, such as fitting a PV array with a higher rated DC output than the inverter's AC output rating.

OZEV landlord chargepoint grants

Also known as Electric vehicle chargepoint grant for landlords, EV chargepoint grant for landlords, Residential landlord chargepoint grant

OZEV (Office for Zero Emission Vehicles) landlord chargepoint grants are UK government grants that help eligible residential landlords pay for EV chargepoint sockets at rented or multi-unit homes.

OZEV renter and flat owner chargepoint grant

Also known as Electric Vehicle Chargepoint Grant for Renters and Flat Owners, EV chargepoint grant for renters and flat owners, Flats and Renters Grant

OZEV (Office for Zero Emission Vehicles) renter and flat owner chargepoint grant is a UK government grant that helps eligible EV drivers who rent their home or own and live in a flat pay for an eligible home chargepoint socket.

P1 port

A P1 port is a local smart-meter data port used on some DSMR (Dutch Smart Meter Requirements) meters to send consumption and export readings to a connected monitoring device.

Panel degradation

Panel degradation is the gradual loss of a solar PV panel's ability to produce power compared with when it was new.

Panel hotspots and bypass diodes

Also known as Panel hotspot, Solar panel hotspot, Photovoltaic module hotspot, Bypass diode

Panel hotspots and bypass diodes are linked solar PV module terms for local cell overheating and the diode path that can limit shading-related heating and output loss.

Parallel batteries

Parallel batteries are compatible battery units, modules or towers configured to work together in the same battery system, usually to increase usable storage capacity within a manufacturer's limits.

Part P

Part P is the electrical-safety part of the Building Regulations for relevant electrical installation work in dwellings.

PAS 2030

Also known as Publicly Available Specification 2030, PAS 2030:2023

PAS 2030 (Publicly Available Specification 2030) is a BSI installation specification for energy efficiency measures in existing dwellings, often seen in retrofit and funded-scheme paperwork.

PAS 2035

Also known as Publicly Available Specification 2035, PAS 2035:2023

PAS 2035 (Publicly Available Specification 2035) is a BSI (British Standards Institution) specification and guidance framework for whole-house energy retrofit work in existing homes.

PAS 63100 battery fire placement

Also known as PAS 63100:2024 battery placement, Publicly Available Specification 63100 battery placement

PAS 63100 battery fire placement is the siting part of PAS 63100 (Publicly Available Specification 63100), which deals with fire-safety placement for domestic battery energy storage systems.

Peak demand

Peak demand is the highest electricity demand reached during a defined period, shown as a power value rather than an energy total.

Peak power

Peak power is the highest power level a device or output can deliver under a stated short-term or maximum condition, usually shown in watts or kilowatts on inverter or battery-system documents.

Peak rate

A peak rate is the unit price that applies during the peak time band of a multi-rate or time-of-use energy tariff.

PEN fault detection

PEN fault detection is the EV charging monitoring used to recognise a possible fault in a combined PEN conductor on a relevant supply.

Penetration

Penetration is a building-fabric opening or route where a cable, pipe, duct, bracket, flue or fixing passes through a roof, wall, floor, ceiling, membrane or fire-separating element.

Performance warranty

A performance warranty is the part of a solar PV module warranty that states how much rated power the module should retain after defined years under the warranty's test and claim conditions.

Permitted development

Permitted development means work or a change of use that is treated as already having planning permission under national permitted development rights, so a separate planning application is not needed when the relevant limits and conditions are met.

Permitted development rights

Permitted development rights are a national grant of planning permission that lets certain building works or changes of use happen without a planning application, provided the relevant limits and conditions are met.

Phase imbalance

Also known as Phase unbalance, Load imbalance

Phase imbalance is an uneven spread of electrical load or generation between the phases of a three-phase supply.

Planning application

A planning application is a formal submission to the local planning authority asking for a decision on proposed development, such as full planning permission, prior approval or a lawful development certificate.

Planning permission

Planning permission is the planning consent that allows development to be carried out. For home energy work, the key question is whether the proposal is already covered by permitted development rights or needs a decision from the local planning authority.

Planning Portal

Planning Portal is an online planning and building control service where people can read guidance, check common project rules and submit many planning-consent or building-control applications.

Plug and Charge

Also known as Plug & Charge, PnC

Plug and Charge is an EV charging feature that lets a compatible vehicle and chargepoint authenticate a charging session automatically, usually through ISO (International Organization for Standardization) 15118 certificate-based communication, rather than relying on a separate RFID card, app or payment card.

PME earthing

Also known as Protective multiple earthing, TN-C-S

PME earthing is a UK supply earthing arrangement where the distributor's neutral and protective functions are combined in the low-voltage network.

Point of connection

Also known as POC, Connection point

A point of connection is the boundary point where a property, installation, generator or controlled load is electrically connected to the distribution network, often shown as POC (point of connection) in DNO paperwork.

Polarity

Also known as Correct polarity, Polarity check, Reverse polarity

Polarity identifies whether conductors or terminals are connected in the expected live, neutral, positive or negative relationship.

Portable air conditioner

Also known as portable AC

A portable air conditioner is a self-contained room appliance that normally rejects heat outdoors through a flexible exhaust hose.

Power

Also known as watts, W

Power is the rate at which electricity or heat is being used, generated, charged, discharged or delivered at a particular moment.

Power export control

Also known as active power export control, export power control, export control

Power export control is an inverter, battery-system or site-controller function that limits active power exported to the distribution network.

Power factor

Also known as PF

Power factor compares active power with apparent power in an AC circuit or device rating.

Power optimiser

Also known as Power optimizer, Solar power optimiser, PV optimiser, PV optimizer, Module-level power optimiser

A power optimiser is solar PV module-level electronics that adjusts DC output from a panel or small module group before it reaches a string inverter.

Pre-installation EICR

Also known as pre installation EICR

A Pre-installation EICR (Electrical Installation Condition Report) is a condition report on the existing fixed electrical installation before proposed home energy work.

Preconditioning

Also known as EV preconditioning, Battery preconditioning

Preconditioning is an EV control that warms or cools the cabin, the traction battery or both before a journey or charging stop, usually from a scheduled departure time, vehicle app or fast-charge preparation setting.

Premium export tariffs tied to installation

Premium export tariffs tied to installation are supplier export tariffs where a higher export rate depends on the customer's import supply, solar or battery installation route or both.

Prepayment meter

A prepayment meter is an electricity or gas meter, or smart-meter mode, where the household adds credit before using energy.

Pressure drop

Pressure drop is the loss of water pressure as heating fluid moves through pipework, heat emitters, valves or other hydraulic components.

Price cap

The price cap is Ofgem's limit on the unit rates and standing charges suppliers can charge households on standard variable gas and electricity tariffs.

Primary circuit

A primary circuit is the heat-source side of a water-based heating system, usually carrying water through a boiler, heat pump or hydraulic separator connection.

Primary pipework sizing

Also known as Pipework sizing, Primary circuit sizing

Primary pipework sizing checks whether the main heating-water pipework can carry the required heat pump flow without excessive pressure drop or velocity.

Product warranty

Also known as Manufacturer warranty, Product guarantee, Limited warranty

A product warranty is a manufacturer's or supplier's written promise about covered faults, defects or remedies for a named item over a stated period and under stated conditions.

Public charging roaming

Public charging roaming lets an EV driver pay for public charging across more than one network through a supported app or RFID card.

PV array

Also known as solar array

A PV array is the group of PV modules installed together as the generating part of a solar PV system.

PV commissioning pack

A PV commissioning pack is the solar-specific handover bundle that records commissioning checks, PV array test results and key documents for a completed solar PV installation.

PV diverter immersion control

Also known as Solar hot water diversion, Solar immersion diverter, PV immersion controller

A PV diverter immersion control uses surplus solar generation to power an immersion heater so a hot water cylinder can be heated before that electricity is exported.

PV fault codes

PV fault codes are numbers, labels or status messages that a solar inverter or monitoring platform uses to identify a detected condition, warning or shutdown reason.

PV module

Also known as solar panel

A PV module is an individual PV panel used as one building block of a PV array.

PV ramp rate

Short-term solar PV output changes, cloud-driven variability and smoothing controls.

PV soiling and cleaning

PV soiling and cleaning describes dirt, bird droppings, pollen, leaves, lichen or other deposits on solar modules and the maintenance step of removing them when they reduce output or breach product guidance.

PV string

Also known as string

A PV string is a series-connected group of solar PV modules that feeds a DC input on an inverter or other PV equipment.

Quote

A quote is a written offer to carry out specified home energy work for an agreed price, setting out the scope, products, costs and conditions before it becomes part of a contract.

R290 propane refrigerant

R290 propane refrigerant is refrigerant-grade propane used in some air source heat pumps as a low-GWP (global warming potential) working fluid.

R32 refrigerant

R32 refrigerant is HFC-32 (hydrofluorocarbon-32), also called difluoromethane, used in some heat pumps and air-conditioning equipment as a sealed-circuit working fluid.

Radiator emitter upgrades

Radiator emitter upgrades are changes to radiators or other room heat emitters so a heating system can deliver the required room heat at the design flow temperature.

Radiator output

Radiator output is the rate at which a radiator can release heat into a room under stated water-temperature, room-temperature and flow conditions.

Randomised delay

Also known as Random delay, Randomised charging delay

Randomised delay is a smart chargepoint function that waits for a short random period before EV charging starts or before the chargepoint changes charging rate.

Rapid charging

Rapid charging is high-power EV charging, usually at a public chargepoint, with UK public statistics treating 50 kW to under 150 kW as rapid.

Rated AC output

Rated AC output is the specified AC-side output power for an inverter or power-conversion device under stated rated conditions.

RCBO / Residual current breaker with overcurrent protection

Also known as Residual current breaker with overcurrent protection, RCBO

Combined residual-current, overload and short-circuit protection for one circuit.

RCD / Residual current device

Also known as Residual current device, RCD

Residual-current protection against electric-shock risk and some fire risk from earth faults.

RDC-DD

Also known as Residual direct current detecting device, RDC-DD

RDC-DD means residual DC detecting device, a Mode 3 EV charging protection device that detects smooth DC residual current so other equipment can disconnect the circuit.

Reactive power control

Reactive power control is the inverter or controller function that changes reactive power or power-factor behaviour to meet a grid, voltage-control or connection setting.

RECC

Also known as Renewable Energy Consumer Code

RECC is the Renewable Energy Consumer Code, a consumer code for businesses selling or leasing small-scale renewable and low-carbon heat or power systems to domestic consumers.

Refrigerant

Refrigerant is the working fluid inside a heat pump or cooling system that absorbs, carries and releases heat as its pressure and temperature change.

Remote monitoring

Remote monitoring is the ability for authorised users, installers or support teams to view a compatible home energy system through an app, portal or service platform while away from the equipment.

Replacing an old boiler

Replacing an old boiler means planning the change from an existing gas, oil, LPG (liquefied petroleum gas) or electric boiler to another heating system, often a heat pump.

Residual current

Also known as earth leakage current

Residual current is the imbalance left when current in a circuit does not return through the same intended conductors that supplied it.

Resistance

Also known as ohms

Resistance is opposition to electric current in a circuit or component, measured in ohms.

Retrofit battery storage

Retrofit battery storage means adding a battery storage system to a property that already has PV generation, an electrical connection, metering, controls or other equipment in place.

Return temperature

Return temperature is the temperature of heating water as it comes back from radiators, underfloor heating or other heat emitters to the heat source.

RFID card

Also known as RFID tag, Charge card, Access card

An RFID card is a physical charging card that identifies an EV driver, account or permission when it is presented to a compatible chargepoint reader.

RoHS and WEEE compliance

RoHS (Restriction of Hazardous Substances) and WEEE (Waste Electrical and Electronic Equipment) compliance describes two product-environment rule areas that may appear on electrical equipment documents.

Roof hook and rail mounting

Also known as Above-roof rail mounting, Roof hook mounting, Solar rail mounting, PV rail mounting

Roof hook and rail mounting is an above-roof solar PV mounting approach where roof hooks or brackets fix the mounting system to the roof structure and rails support the modules above the roof covering.

Roof loading

Roof loading is the weight and force that a roof structure must safely carry, including existing roof materials, weather loads and any added equipment or ballast.

Roof pitch

Also known as roof slope

Roof pitch is the angle or steepness of a roof surface, usually measured from horizontal in solar PV documents.

Room schedule

Also known as room schedules, room-by-room schedule, room data sheet, room data sheets, heat loss room schedule

A room schedule is a table or document that lists rooms or spaces in a property and records the room-level details needed for a design, survey or handover pack.

Room thermostat

A room thermostat is a heating control that senses air temperature in a room or zone and sends a demand or set-point signal to the heating system.

Room-by-room heat loss

Also known as room by room heat loss, specific room heat loss

Room-by-room heat loss is a heat-pump design calculation that estimates how much heat each individual room loses under stated design conditions.

Rotary isolator

Also known as Rotary isolation switch

A rotary isolator is an isolation switch with a rotating handle, used to disconnect an electrical supply from equipment or a circuit rather than proving the installation is safe.

Round-trip efficiency

Battery storage efficiency across a defined charge and discharge path.

RS485

Also known as RS-485, EIA-485, TIA/EIA-485

RS485 (Recommended Standard 485) is a wired serial communication interface used by compatible inverters, meters, data loggers and controllers to exchange data over differential signal lines.

Scaffold

A scaffold is a temporary access structure used to reach or work at height, such as around a roof, wall or other elevated part of a home energy installation.

Scheduled charge

Also known as Timed charge, Scheduled charging

Scheduled charge is a planned battery-charging window set in an app, inverter or energy-management control.

Scheduled discharge

Also known as Timed discharge

Scheduled discharge is a planned battery-discharge window set in an app, inverter or energy-management control.

Schematic

A schematic is a simplified technical diagram that shows how the main parts of a home energy system are connected or arranged.

SCOP (seasonal coefficient of performance)

Also known as Seasonal coefficient of performance, SCOP

Heat pump seasonal efficiency rating across a designated heating season, distinct from a single-point COP and from design-specific SPF estimates.

Seasonal heat pump maintenance

Also known as Heat pump seasonal maintenance

Seasonal heat pump maintenance is the recurring set of product-specific checks and servicing tasks carried out around a heat pump's heating season.

Seasonal performance factor

Also known as SPF

Seasonal performance factor, or SPF, describes how efficiently a heat pump system is expected or measured to work over a season rather than at one test point.

Secondary circuit

A secondary circuit is the heating-water circuit on the load side of a primary heat source, hydraulic separator or low-loss header.

SEER

Also known as seasonal energy efficiency ratio

SEER is a seasonal product metric for cooling efficiency under a defined test method.

SEG (Smart Export Guarantee)

Also known as SEG

The SEG is the Great Britain scheme under which participating electricity suppliers pay eligible small-scale low-carbon generators for electricity exported to the grid.

Self-consumption

Self-consumption is solar PV electricity used by the property instead of being exported to the distribution network.

Self-sufficiency

Self-sufficiency is the share of a property's electricity use that is met by its own solar PV generation or electrical storage.

Self-use mode

Self-use mode is an inverter or battery operating mode that gives priority to using on-site solar electricity in the home before charging the battery or exporting surplus.

Serial number

Also known as S/N

A serial number is a unique identifier assigned to one physical device or component, often printed on its label and used in support, registration, warranty and recall workflows.

Service access

Service access is the space, route and reachability left so equipment can be inspected, operated, maintained or repaired after it has been installed.

Service head

Also known as Cut-out

Service-head wording refers to the distributor or supplier intake equipment where the service cable and main supply fuse meet the property, not proof that the supply can support extra load.

Service record

Also known as Service history, Servicing record, Maintenance record

A service record is a written log of maintenance, inspection, servicing or repair work that has already been carried out on an installed home energy system.

Setback

Setback is a heating-control setting that uses a lower target temperature for a scheduled period rather than turning heating fully off.

Settlement period

A settlement period is one half-hour block used in Great Britain electricity trading and settlement to match meter data, forecasts and supplier accounting to a specific interval.

Shading

Shading is sunlight being blocked from part or all of a solar PV module or array.

Shading analysis

Shading analysis is the assessment of how nearby or distant objects are expected to reduce sunlight reaching a proposed solar PV array.

Shading report

A shading report records how shade is expected to affect a solar PV array and its generation estimate.

Shared ground loop systems

Also known as Shared ground loop, Shared ground loops, Networked ground source heat pumps

Shared ground loop systems are ground source heat pump arrangements where a shared buried loop or borehole array supplies low-temperature heat to individual heat pumps in more than one home or flat.

Short circuit

Short circuit is an electrical fault where an unintended conductive path lets current flow between parts that should not be connected.

Short cycling

Short cycling is repeated brief on-off running, where a heat pump starts, stops and starts again more often than the heating load or control sequence should require.

Short-circuit current

Also known as Isc

Short-circuit current is the current that flows when a short circuit is present, and in solar PV documents it often appears as the Isc rating for a module or string under stated test conditions.

Single-line diagram

Also known as SLD

A single-line diagram is a simplified electrical drawing that shows the main connection path between the grid, protection devices and home energy equipment.

Single-phase charging

Single-phase charging is AC EV charging that uses one phase of the electricity supply, commonly seen in UK home chargepoint material at around 7 kW.

Single-phase supply

Also known as single phase

A single-phase supply is a property electricity supply that uses one live phase and neutral for the normal low-voltage connection.

Single-split system

Also known as single split

A single-split system connects one fixed indoor AC unit to one outdoor unit.

Site export control

Site export control is the site-level control function that limits how much electricity a property sends to the distribution network.

Smart Charge Points Regulations

The Smart Charge Points Regulations are the Great Britain rules that require many private EV charge points and smart charging cables sold for domestic or workplace use to include smart functions and device-level protections.

Smart charging

Smart charging is EV charging that can automatically change when or how quickly electricity flows, usually so a compatible charger, vehicle or service can charge at lower-demand, cheaper or renewable-rich times.

Smart export meter exchange timing

Smart export meter exchange timing is the setup period while a supplier confirms that the meter can provide half-hourly export readings, arranges a suitable smart or export meter if needed and links the installation to an export MPAN before SEG payments can start.

Smart meter

A smart meter is a gas or electricity meter that records energy use digitally and can send meter readings automatically to the supplier through the smart-meter network.

SMETS1

SMETS1 is the first-generation smart-meter standard for Great Britain, used for older smart gas or electricity meters installed before the later SMETS2 rollout.

SMETS2 / Second-generation smart meter standard

Also known as Second-generation smart meter standard, SMETS2

Second-generation UK smart metering standard for current domestic smart meters, supplier switching and smart-tariff meter communications.

Soakaway

A soakaway is a drainage feature that lets rainwater, surface water or heat pump condensate soak into suitable ground instead of flowing straight to a watercourse or sewer.

Solar charging

Solar charging means using on-site solar PV generation as the charging source for a home battery, EV or other compatible load.

Solar divert charging

Solar divert charging is EV charging that tries to use surplus on-site solar PV generation by changing, pausing or supplementing the charge session according to available generation or site import and export data.

Solar forecast

Also known as PV forecast, solar PV forecast, solar generation forecast

A solar forecast estimates how much electricity a solar PV system may generate over a future period, using weather data and site details rather than measured output.

Solar PV

Also known as photovoltaics, PV

Solar PV uses PV modules or panels to convert sunlight into DC electricity as part of a wider solar PV system.

Solar self-consumption estimates

A solar self-consumption estimate forecasts how much generated solar PV electricity a property is expected to use on site rather than export.

Solar yield

Solar yield is the amount of electricity a solar PV system produces over a period, usually recorded in kWh and sometimes compared as kWh per kWp.

Solid wall insulation

Solid wall insulation is insulation added to the inside or outside of a solid external wall to reduce heat loss through that wall.

Sound power level

Sound power level is a rating of the total sound energy a heat pump or other source radiates, usually shown in dB(A) for product data and noise calculations.

Sound pressure level

Sound pressure level is the sound level at a particular point, usually given in dB or dB(A), after the source sound, distance, reflecting surfaces and barriers have affected what reaches that position.

Specific yield

Specific yield is a solar PV output figure that shows generated electricity per installed kWp (kilowatt peak), usually in kWh/kWp.

Specification

A specification is a written technical description of the products, system design, requirements or limits that a home energy proposal or installation is expected to meet.

Split system

A split system separates the refrigerant equipment into outdoor and indoor units connected by refrigerant pipework.

Standard test conditions

Also known as STC

Standard test conditions are the laboratory conditions used to rate solar PV modules, usually shortened to STC on datasheets and module labels.

Standing charge

A standing charge is the fixed daily charge on an energy tariff, paid for each day of supply as well as any unit-rate charges for energy used.

State of charge

Also known as SOC

State of charge, or SOC, is the current charge level of a battery, usually shown as a percentage.

State of charge control

State of charge control is the way a battery or inverter sets minimum reserve levels, charge targets or operating ranges around a battery's state of charge.

State of health

Also known as SOH

State of health, or SOH, is a battery condition measure that compares the battery with its original or rated condition.

Static load limit

Static load limit is a fixed current or power cap set for an EV charger or charging group so charging stays within a chosen maximum instead of changing automatically with live household demand.

String design voltage windows

String design voltage windows are the DC voltage ranges a proposed solar PV string must stay within when it is matched to an inverter or MPPT input.

String inverter

A string inverter is a solar PV inverter that converts DC from one or more PV module strings into AC for the installation.

String layout

String layout is the plan for how solar PV modules are divided into one or more series strings and connected to inverter or MPPT inputs.

String voltage

String voltage is the DC voltage across a connected solar PV string, usually set by the module voltages added together in series.

Structural survey

A structural survey is a check of whether part of a building, such as a roof, wall or floor, can safely carry existing loads and any proposed home energy equipment.

Supplier of last resort process

Also known as Supplier of Last Resort, SoLR, SoLR process

The supplier of last resort process is Ofgem's safety-net process for appointing a new energy supplier when a gas or electricity supplier fails.

Surge protective device

Also known as SPD

A surge protective device is a protective electrical device that limits transient overvoltage so a surge is less likely to damage connected equipment.

SWA cable

Also known as Steel wire armoured cable

SWA (steel wire armoured) cable is a fixed-wiring cable with steel wire armour around the insulated cores for mechanical protection.

Switching mechanics across suppliers

Switching mechanics across suppliers describes the administrative steps, timings and consumer protections used when a household moves a gas or electricity account from one energy supplier to another.

T.O.U. / Time-of-use tariff

Also known as Time-of-use tariff, TOU

Electricity tariff pricing that varies by time period, including off-peak and peak rates, Economy 7 style windows and smart tariffs.

Tariff mode

Also known as Time-of-use mode, TOU mode

Tariff mode is a battery or inverter operating mode that uses electricity tariff periods or rates to guide when the battery charges, holds or discharges.

Tariff stacking

Tariff stacking is the practice of checking how a household's import tariff, export tariff and managed-load rewards work together before relying on the combined value.

Tariff window

A tariff window is the period when a particular unit rate, export payment condition or smart-tariff schedule applies under an energy tariff.

Telemetry

Telemetry is automatically measured or reported data sent from equipment, sensors or controls to an app, portal, API (application programming interface) or service for monitoring, analysis or system control.

Temperature coefficient

A temperature coefficient shows how a solar PV module rating changes as the module or cell temperature changes from the stated test condition.

Tethered charger

A tethered charger is an EV chargepoint with its charging cable fixed to the unit, so the driver uses the attached cable rather than a separate lead from a socketed charger.

Thermal runaway

Thermal runaway is an uncontrolled self-heating failure state in a battery cell where heat builds faster than it can escape.

Thermal runaway containment

Thermal runaway containment is the battery-unit, enclosure, control or installation design intended to limit the spread or effects of a thermal runaway event in a BESS (battery energy storage system).

Thermal store

A thermal store is an insulated vessel that stores heat in water so a heating system can use that heat later for space heating or hot water.

Thermostatic radiator valve

Also known as TRV

A thermostatic radiator valve is a self-regulating radiator control that adjusts hot-water flow through one radiator as the room around the valve warms or cools.

Three-phase charging

Three-phase charging is AC EV charging that uses a three-phase electrical supply, usually so a compatible chargepoint and vehicle can charge at a higher AC power than a single-phase home charger.

Three-phase supply

Also known as three phase

A three-phase supply is a property electricity supply served by three live phases rather than one, so loads and generation can be considered per phase.

Three-phase supply upgrades

Also known as three phase upgrade

A three-phase supply upgrade is a change to an existing electricity connection so the property can use a three-phase supply or higher three-phase capacity.

Three-pin charging

Also known as 3-pin charging, Three pin charging, 3 pin charging, 13A socket charging, Granny charging

Three-pin charging is EV charging from a standard UK 13 A three-pin mains socket using a portable Mode 2 charging lead rather than a fixed Mode 3 home chargepoint.

Tilt

Tilt is the angle of a solar PV module or array from the horizontal plane, usually stated in degrees.

Time-based control

Time-based control is a battery or inverter control approach that uses clock times or scheduled windows to decide when the system charges, holds or discharges.

Time-of-use battery arbitrage

Time-of-use battery arbitrage means using a home battery to shift grid electricity from lower-price tariff periods to higher-price household-use periods.

Transfer switch

A transfer switch changes selected circuits or a backup arrangement from the normal grid supply to an alternative supply such as a battery inverter's backup or EPS output.

Transmission network

The transmission network is the high-voltage electricity network that moves large amounts of electricity over long distances before it passes into local distribution networks.

TrustMark

TrustMark is the UK Government-endorsed quality scheme for businesses carrying out work in or around the home, including some home energy and retrofit work.

TT earthing

Also known as TT system

TT earthing is an earthing arrangement where the installation uses its own earth electrode instead of relying on a TN earthing connection from the distributor.

Twin and earth cable

Also known as T&E, Twin & Earth cable, 6242Y cable

Twin and earth cable is a flat fixed-wiring cable, often labelled T&E (twin and earth), with insulated live conductors and a circuit protective conductor inside an outer sheath.

Type 2 cable

A Type 2 cable is an EV charging lead used with Type 2 AC charging equipment, usually as the separate lead between a socketed chargepoint and a vehicle with a compatible inlet.

Type 2 connector

A Type 2 connector is the AC EV connector standard used on many UK and European home and public chargepoints, charging cables and vehicle inlets.

Type 2 socket

A Type 2 socket is the socket outlet on an AC EV chargepoint that accepts a separate Type 2 charging cable instead of using a cable fixed to the charger.

Type A RCD

A Type A RCD is a residual current device type intended to operate with AC residual current and pulsating DC residual current.

Type B RCD

A Type B RCD is a residual current device type intended to operate with AC, pulsating DC and smooth DC residual currents in suitable AC installations.

Type F RCD

A Type F RCD (residual current device) is a residual-current device type that extends Type A behaviour for specified AC and DC residual-current components.

Type-tested inverter

A type-tested inverter is an inverter whose manufacturer has tested and documented the product against the relevant GB grid-connection requirements.

UKCA and CE marking transition

UKCA (UK Conformity Assessed) and CE (Conformité Européenne) marking transition describes the product-marking period after the United Kingdom left the European Union, in which Great Britain accepts CE marking for many product rules while UKCA marking remains available.

Ultra-rapid charging

Ultra-rapid charging is a public EV charging power-band label, with GOV.UK public charging statistics treating 150 kW and above as ultra-rapid.

Underfloor heating

Also known as UFH

Underfloor heating is a heat-emitter arrangement that uses pipework loops or electric heating elements in the floor so the floor surface releases heat into the room.

Underfloor heating compatibility

Also known as UFH compatibility

Underfloor heating compatibility checks whether a floor heating system can deliver the required room heat at the flow temperature and controls a heat pump or heating design expects.

Uninterruptible power supply

Also known as UPS

An uninterruptible power supply is a battery-backed power unit or system designed to keep a connected load supplied automatically when the incoming mains supply is interrupted.

Unit rate

A unit rate is the price charged or paid for each unit of energy, usually shown as pence per kilowatt hour on an energy tariff, bill or export payment page.

Untethered charger

An untethered charger is an EV chargepoint without a fixed charging cable, so the driver connects the vehicle with a separate compatible cable plugged into the charger socket.

Usable capacity

Also known as Usable energy

Usable capacity is the amount of stored energy a battery system makes available for normal operation.

User manual

A user manual is the customer-facing document that explains how to use, monitor and look after a specific product or system after it has been installed.

Variable tariff

A variable tariff is an energy import tariff where the unit rate or standing charge can change rather than staying fixed for a set contract period.

Vehicle-grid integration

Also known as VGI

VGI (vehicle-grid integration) describes the coordination of EV charging, chargepoints and electricity networks so charging demand and, where supported, vehicle-battery export can be managed with grid conditions.

Vehicle-to-grid

Also known as V2G, Vehicle-to-grid charging

Vehicle-to-grid is bidirectional EV charging that can discharge electricity from a compatible vehicle battery through a suitable chargepoint back to the electricity network.

Vehicle-to-home

Also known as V2H, Vehicle-to-home charging

Vehicle-to-home is bidirectional EV charging that can discharge electricity from a compatible vehicle battery through a suitable chargepoint for use in the home.

Vehicle-to-load

Also known as V2L, Vehicle-to-load power

Vehicle-to-load is an EV function that lets a compatible vehicle battery supply electricity to a connected load, usually through a vehicle socket or adaptor, rather than sending power to a home installation or the grid.

Ventilation

Ventilation is the planned movement of air through a room, building space or equipment location to remove stale air, moisture, pollutants or heat.

Ventilation rate

Ventilation rate is the amount of air a room, dwelling or other defined space is designed or measured to supply, extract or exchange over a given time.

Virtual power plant

Also known as VPP

A virtual power plant (VPP) is a software-controlled group of small energy assets, such as home batteries, solar systems, EVs or flexible loads, coordinated to act like one resource for a supplier, aggregator or grid service.

Voltage

Also known as V, volts

Voltage is the electrical potential difference, measured in volts, that describes supply levels, equipment ratings and battery operating ranges.

Voltage at maximum power

Also known as Vmp

Voltage at maximum power is the PV module, string or array voltage at the maximum power point, usually shown as Vmp (voltage at maximum power) on solar datasheets.

Voltage complaint

A voltage complaint is a report to an electricity distributor that the supply voltage at a premises may be outside the permitted range.

Voltage drop

Voltage drop is the reduction in voltage between two points in a circuit when current flows through cable or equipment impedance.

Voltage rise

Voltage rise is the increase in voltage that can occur when generation or export pushes electricity back through a cable or local network.

Volumiser

A volumiser is a water vessel added to a heat pump heating circuit to increase the heating-system volume without necessarily acting as a hydraulic separator.

Warranty document

A warranty document sets out the written warranty or guarantee terms for home energy equipment, workmanship or related financial protection.

Warranty exclusion

A warranty exclusion is wording in a warranty document that states situations, faults or actions the warranty does not cover.

Warranty registration

Warranty registration is the step of recording a product, installation or workmanship guarantee with the responsible manufacturer, installer, scheme operator or warranty provider.

Warranty throughput

Also known as Warranty energy throughput, Throughput allowance, Aggregate throughput

Warranty throughput is the cumulative energy-use figure that a battery warranty counts against a stated use limit or warranty condition.

Water source heat pump

Also known as WSHP

A water source heat pump is a heat pump that extracts low-temperature heat from a water source such as a lake, pond or river.

Weather compensation

Weather compensation is a heating-control function that changes the heating-system flow temperature in response to outdoor conditions.

Whole-home backup

Also known as Whole-property backup, Whole house backup, Full property backup

Whole-home backup is a backup arrangement intended to make the whole property the backed-up part of the installation during a grid outage, rather than only selected essential loads.

Wi-Fi dongle

Also known as WiFi dongle, Wi-Fi datalogger, Wi-Fi stick, Monitoring stick

A Wi-Fi dongle is a plug-in communication adapter that lets compatible inverters, batteries or gateways connect to a local Wi-Fi network for monitoring, setup or service-platform data exchange.

Wide area network

Also known as WAN

A WAN (wide area network) is the smart-meter communications path that links a property's communications hub to the DCC smart meter network rather than to the household's Wi-Fi.

Wind uplift

Wind uplift is the upward lifting force that wind can place on roof-mounted equipment, mounting rails, fixings or roof coverings.

Workmanship warranty

A workmanship warranty is cover for faults caused by the way installation work was carried out, separate from product warranties for the equipment itself.

Zero export

Also known as zero-export, zero export setting, zero net export

Zero export is an export-control setting or arrangement that aims to keep a property's net export to the distribution network at zero.

Zero-rated VAT on energy-saving materials

Also known as 0% VAT on energy-saving materials, VAT relief on energy-saving materials

Zero-rated VAT (Value Added Tax) on energy-saving materials is the temporary UK VAT relief that charges 0% on the installation of specified materials such as solar panels, heat pumps, electrical storage batteries and smart diverters when the HMRC conditions are met.

Zoning

Zoning is a heating-control arrangement that divides a home or heating system into separately controlled areas rather than treating the whole property as one space.